1. Field of the Invention
The present invention relates to the field of labels which are provided without separation liners between the labels and layers of supply of labels, and rolls, especially linerless labels provided in roll form. The present invention also relates to apparatus and methods for applying linerless labels to substrates.
2. Background of the Invention
Labels which are not provided to commerce with liners over an adhesive face, referred to in the art as linerless labels, are less expensive than linered labels, more labels can be provided in a roll of a given diameter than conventional labels with release liners, and they are more environmentally friendly since they do not require the disposal of liners after use. Linerless labels should also be less expensive since one entire element (the liner) may be removed from the manufacturing cost of the label. Liners can constitute 35% to 50% of the total cost of a linered label construction. For these and other reasons, linerless labels are achieving increased popularity. Equipment for applying linerless with rewettable or thermal sensitive adhesives to a wide variety of moving elements (such as substrates, bottles, or packages) is fairly common, as shown in U.S. Pat. Nos. 2,492,908 and 4,468,274. However, the application of unlinered pressure sensitive adhesive labels to moving elements although known in the art, is uncommon (e.g., U.S. Pat. No. 4,978,415), and does not have the versatility to apply the labels to all sorts of moving elements, such as envelopes, webs, bottles, cans, and packages.
According to U.S. Pat. No. 5,674,345, a method and apparatus are provided which quickly, positively, and in a versatile manner apply linerless pressure sensitive adhesive labels to moving elements. The equipment and method are versatile since they may be utilized with envelopes, packages, substrates, bottles, cans, packages and a wide variety of other moving elements, and the method and apparatus typically are practiced so as to leave no skeletal web after the labels are formed, thus avoiding any necessity of disposing of any waste label material. According to the apparatus of that invention, means for mounting a supply of linerless label tape having a release coated face and adhesive (typically pressure sensitive adhesive) face is associated with a number of novel apparatus elements according to the invention. These novel elements include a non-stick circumferential surface feed roll, a hardened vacuum anvil cylinder cooperating with a cutting cylinder having a radially extending knife blade, which in turn cooperates with a wiper roller that applies liquid release material to the blade after each cut, and transport means having many unique features. The transport means includes a plurality of conveyor tapes which are spaced in a direction transverse to the direction of conveyance of labels thereby, and a vacuum chamber assists the adhesive from the labels in maintaining the labels in position on the conveyor tapes during conveyance. The conveyor tapes are typically substantially circular in cross section so as to present a minimal area for engagement with the label adhesive, and the labels are separated from the conveyor tapes by a plurality of non-stick surface stripper rings which extend upwardly above the top surface of the conveyor tapes, and are associated with a peeler roller which bends the labels upwardly as they are deflected by the stripper rings. From the peeler roller and stripper rings the labels are moved directly into contact with a moving element. Where, as typical, the labels are moved into contact with moving envelopes, the labels and envelopes pass through nip rollers whereby the pressure sensitive adhesive is activated.
Linerless labels have also become increasingly more popular because of the many advantages associated therewith. When any labels, including linerless labels, are used, it also is necessary to be able to automatically print the labels in a cost-effective manner. One way this can readily be accomplished is by using a thermal printer, either a thermal printer having a thermal printhead with a thermal ribbon unwind and rewind system, or a thermal printer with a direct thermal printhead. Conventional thermal printers are not capable of printing linerless labels, however, because there will be surfaces thereof which necessarily come into contact with the uncovered adhesive face of the linerless labels as the labels are being fed to the printhead, during printing, or afterwards. According to U.S. Pat. No. 5,560,293, a variety of thermal printers are provided which overcome this problem and are eminently suited for effective printing of linerless labels. The linerless labels printed according to the present invention may be almost any type of linerless labels, such as for examples, thermal ribbon embodiments shown in U.S. Pat. No. 5,354,588 and direct thermal printer embodiments such as shown in U.S. Pat. No. 5,292,713.
U.S. Pat. No. 5,560,293 describes a thermal printer which prints linerless labels in such a way that printer components will not stick to the adhesive face of linerless labels. Substantially stationary printer components, such as a label guide, transport plate, front panel, and stripper blade, preferably have the adhesive face engaging surfaces thereof plasma coated so that adhesive will not stick to them. An optional cutter provided downstream of the stripper blade also has plasma coated surfaces. A driven platen roller has a surface thereof coated with or covered by a high release silicone, which will not stick to the adhesive, but has high friction characteristics to facilitate drive of the labels. In a direct thermal printer, a plasma coated tear off surface is downstream of the driven platen roller, and stripper belts, a second roller with O-rings, and the like are provided to prevent the labels from wrapping around the driven platen roller. One or more sensors may also be provided for controlling drive of the platen roller in response to the position of registration marks on the linerless labels. According to one aspect of that invention a thermal printer for printing linerless labels, having an uncovered adhesive face, is provided comprising the following elements: a linerless label unwind; a substantially stationary label guide; a substantially stationary transport plate; a rotatable driven platen roller; a printhead cooperating with the print roller; and, the label guide and transport plate having surfaces which engage the adhesive face of linerless labels from the label unwind, the adhesive-engaging surfaces comprising plasma coated surfaces which substantially prevent the label adhesive from adhering thereto. The printhead preferably comprises a thermal printhead, and a thermal printer unwind and rewind system is associated with the printhead that provides the thermal ribbon between the printhead and the driven platen roller. The driven platen roller preferably has a peripheral surface thereof which is coated with a high release silicone which has both non-stick characteristics with respect to the adhesive face of the linerless labels, but also high friction characteristics to facilitate driving of the labels. Any other substantially stationary surfaces of the printer which are also likely to come into contact with the adhesive face of the linerless labels-such as a front panel-are also plasma coated. The transport plate may be grooved to minimize the surface area that engages the label adhesive face. The printer also preferably comprises a stripper blade/bridge mounted on the opposite side of the driven platen roller from the label unwind, in the direction of label conveyance through the printer. The stripper blade/bridge is positioned with respect to the driven platen roller and the printhead so as to prevent a printed label from being wound onto the driven platen roller and assists the label moving from the platen roller to the cutter. The stripper blade/bridge has a surface which has a non-stick feature, preferably a plasma coating, and typically the stripper blade/bridge may be mounted directly on a pre-existing tear bar on the printer. According to that invention a conventional thermal printer may readily be modified merely by substituting the particular non-stick label guide, transport plate, and driven platen roller according to the invention, and mounting the stripper blade/bridge on the existing tear bar.
Linerless labels are produced, for example, by feeding a tape having a release coated face and an adhesive face to a hardened anvil vacuum cylinder, utilizing a non-stick circumferential surface feed roll. A knife blade on a cutting cylinder is rotated into contact with the tape at the anvil cylinder to cut the tape into linerless labels, and release liquid is applied to the blade after each cut. From the anvil cylinder the labels are deposited on a plurality of spaced conveyor tapes of circular cross section with the adhesive faces contacting the conveyor tapes. A vacuum chamber assists in holding the labels on the conveyor tapes. The release coat faces of the labels conveyed by the conveyor tapes may be heated and then printed with hot melt ink from an ink jet printer. The labels are separated from the conveyor tapes using a peeler roll and non-stick stripper rings, and then immediately contact a moving web or other elements to which they are to be applied, with the label and web passing through nip rolls to activate the pressure sensitive adhesive.
In spite of the benefits which are obvious from the proposed and actual use of linerless labels, the growth of the technology has not been as rapid in commerce as has been expected. The reduced rate of acceptance is due at least in part because the present capability of application equipment is significantly slower than for linered labels. In production and supply, faster rates without waste are critical to levels of efficiency, productivity and profitability. Significantly slower equipment, such as the present linerless label application systems which operate at speeds one fourth to one half the speed of linered label applicators, reduce cost competitive aspects of the linerless label. Additionally, the cost of equipment specific to linerless labels requires an independent capital investment for equipment which is useful only for the linerless labels. For a manufacturer to convert from a linered label process or to add a linered label process to his business, a completely new apparatus has to be purchased. At a cost of hundreds of thousands of dollars, this is not a highly attractive scenario for labeling companies.